Air oxidation of isobutylene



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[SOC- 200 C Scrubber Pressure 300 psi Feb- 5, N, C, ROBERTSON ETAL AIR OXIDATION OF ISOBUTYLENE Filed Oct. 22, 1952 2 Sheets-Sheet 1 {Pressure Relief Valve Venl' Cooling Condenser Disl'illcl'ipn Reaclion sobul'yle ne Reac'l'ion Producls Iso bul'ylene 7 solvcnl' (e.g. Terfiury Bu'l'yl Alcohol.)

+Isobu+y|ene Air FIG. I

IN VEN TOR5 NAT C. ROBERTSON BY JAMES H. GARDNER ATTORNEY Feb. 5, 1957 N. C. ROBERTSON ET AL AIR OXIDATION OF ISOBUTYLENE Filed Oct. 22, 1952 Heqi'er m Reflux -Isobu+ane Isobu+ylene olvenf Ter-Hory Buiyl Alcohol 2 Sheets-Sheet 2 Cooling l2 Condenser {Pressure Isobui'ane 3 Relief Valve Ven+ Producfs Wai'er 0m w. MN

ATTORNEY United States Patent Chemical Corporation, Pace, Fla., a corporation of Delaware Application O'ctober;22, 1952*, Serial No. 316,158"- 1 Claim-., (Cl. 260-635) This invention@ relates: to theproduction of chemicals andinore particularly' to lhC PlOdllCllOILOf glycolsa A principal: object. of: the: present invention=-is1 to pro duceiglycols in goodyields by the.- liquid-phase oxidation of normally gaseous hydrocarbons in an organicsolvent with an elemental-oxygen-containinggas:

Another-object of the invention is to provide a process of the above type which is particularly adapted to the production of iso-butylene glycol by theoxidation of isobutylene.

Still another object of the invention is to provide an integrated proces's which produces high-yieldsof isobutyl ene glycol when utilizing v isobutane as a starting'materia'l and air as the oxidizing :agent.

Other objects-of the invention will in part be obvious and 'will in part appear hereinafter.

The invention accordingly comprises the processinvolving-the several steps and the relation and the order of'one or more of such steps with re'spect toeach of the others which are exemplified in the following detailed disclosure, and. the scope of the application of'wwhich will beindicated in the claims.

For a fuller understanding; of the nature and objects ofthe invention; reference should be had to the following detailed description taken in connectionwith the accompanying drawings wherein:

Fig. 1 is a diagrammatic flow sheet illustratingone embodiment of the invention; and

Fig. 2 is a diagrammatic flow sheetillustrating another embodiment of the invention. V

In the present invention a normally gaseous hydrocarbon; is converted to the-corresponding glycol by oxidation in the liquid phase at a relatively high pressure. In one preferred embodiment of the invention the gaseous hydrocarbon is an unsaturatedv aliphatic compound; a particular preferred embodiment including'isobutylene. as the hydrocarbon to be'converted' tothe glycol; In order to obtain a high-yield of the glycol, it is desiredithat the pH of the solution be maintained on the'order'of -at least 5 or above. This has the advantage that, during oxidation, few acids are formed, it being believed that" the formation of acids leads to degradation of the products. This pH is preferably maintained at 5 or. above by the use of a buffer solution which is maintained in sufiicient concentration to neutralize any acids formed. It is also preferable that the oxygen fed to the reactor becont'rolledso that no excess oxygen exists ,abovethe-reaetion mixture. This has the advantage of both diminishingthe possibility of obtaining hazardous concentrationsofexplosive gases and also of preventing excessive oxidation of the isobutylene glycol which is thedesiredproduct of the reaction.

In a preferred embodiment of the invention the conditions of reaction are so adjusted thatpolymerizatidn.of the-.-feedand/or the various intermediate .by.-pI'Odl.lCtS. of the reaction is minimized; In one aspect of'the inventionpolymerization is substantially eliminated" by 'the 2,780,654 Fatented: Feb. 5,. 19.57%

use-of a low concentration of the olefin-its thesqlvent;

For example,- it has-been found that, when the molepeb cent of; the-olefin is less than about 30% of thesolvent during -theoxidation, the creation of undesirable poly meric by-products is minimized. In another embodiment of the invention, the elimination ofpolymeric' materials may be achieved; by the, use, of inhibitors; one preferred type ot inhibitor; being: nitrobenzene.

- In; another, embodiment; of. the invention;. the. gaseous hydrocarbon: used; aspa. startingmaterial is. a: saturated aliphatic: hydrocarbon; in. particular 1 isobutane,-. thev i509 butane being; converted to isobutylene. which; is: subsequentlyoxidizedltoeisobutylene.glycoL.

Thesinvention: will befirst described in connectionwith the oxidation ofisohutyleneto isobutylene glycol, itxbeing understood. thatitheinvention is by no; means limited; by this-specific illustration; This preferred embodiment of the invention is set forth-in the following nonlimiting example.-

- Example I 972 grams of a mixture of tertiary butyl alcohol and 810grams H2O (as a solvent) together with 1.7 grams ofa. manganese propionate catalyst and 40 cc. of'apH 5 phosphate buffer solution are charged to. a highpressure reactor 10'. 1 gramsflof isobutylene are now passed into thereactor 10'and the temperature thereofisraised to about C. Air is fed into the reactor untilthe pressure. reaches 69.0 710 p. s.- i., the temperature being raised' to, -l,80, C. during thisaddition. Asteady rate} of air, feed of, about four, standardcubic, fetper hour is commenced An automatic pressure relief. valve, vents nitrogen, oxidesof carbon, and a smallamountof uncondensed reactant downstreamof a condenser 12. to maintain 700 p. s. i. in they reactor. Isobutylene is fed at varying ratesvto. roughly replenish theconsumption. 60 grams of'isobutylene are fed, in this. manner during a six hour run.

After terminationof therun, thereaction: mixture is neutralized and fractionated. to obtain-the following ma terials, indicated, asgramsof product. per 100 grams of isobutylene consumed:

Acetone 27.6 grams; methalyl alcohol-4.96 grams; isobutylene glycol 56.1 grams; formic acid 17.4 grams; acetic acid 4.34 grams;. isobutyric acid 10.60 grams;.methanol 0.83 gram; 2 butanone 17.7grams methylacetatenlz47 grams; isobutyl acetate 0.51 gram; carbon monoxide 4.21 grams; carbon,dioxid e.z7.35 grams; and polymeric. mate rial 13.5 grams. In this specific example.222.grams of product wereobtained and, 158-grams of isobutylene were consumed.

In the above, specific example the concentratiomohthe olefin is rather leauduring theoxidation. Whilen'ot essential'to the. operation ofthe process, this,aspectiof the invention has been found to greatly decrease. the amount of polymeric material produced per hundred grams of olefin consumed- In this connection it has-been found that best results are. achieved. when the. mole-.percent ofthe olefin in the reaction zone is maintaineddess than about 30% of the reaction mass. Thisconcentrati'on is preferably less than about 20% and in the aboveexam ple was actually maintained below 151% In the above example thevsolvent. wasillustrated as. a mixture of water and tertiary butyl alcohol. Equally good results are obtained if tertiary butyl alcohol is used alone as the solvent. Benzene and other organiczsolve-nts can be utilized-inplace ofthe tertiarybutylalcohol.

One example ofthe .use of benzeneiasan alternate sol-f benzene as the solvent in place of the tertiary butyl alcohol used in Example I. The same conditions (of temperature, pressure catalyst, etc.) existed here as above. However, the concentration of isobutylene was about 42 mole percent of the amount of solvent. The products obtained from this reaction were isolated and determined to exist in the following concentrations (indicated as grams of product per hundred grams of isobutylene consumed):

Acetone 17.0 grams; tertiary butyl alcohol 2.6 grams; methallyl alcohol 1.4 grams; isobutylene glycol 29.4 grams; formic acid 8.3 grams; acetic acid 1.6 grams; isobutyric acid 1.2 grams; methanol 1.9 grams; 2-butanone 4.3 grams; mesityl oxide 2.4 grams; isobutyl acetate 4.2 grams; carbon monoxide 3.7 grams; carbon dioxide 2.7 grams; and polymeric material 49.8 grams.

As will be noted, the amount of polymeric material produced in this Example II is considerably in excess of the amount obtained in Example I. The formation of this polymeric material can be substantially inhibited by maintaining the olefin concentration low in the reaction mass in the same manner as discussed in connection with Example I. Naturally, inhibition of the polymer formations is desirable but is not necessarily essential to the commercial utility of the process.

When the process is operated on a continuous basis, the condenser 12 continuously refluxes isobutylene, isobutylene glycol and other oxygenated products to a water scrubber 14. The refluxed isobutylene is separated from the remainder of the reflux in the scrubber 14 and is recycled to the bottom of the reactor 10. From the scrubber 14 the reflux and the scrub water are directed into a distillation separation apparatus 16 (which may include several conventional styles) where the contained water and various reaction products are removed from the solvent (e. g., benzene or tertiary butyl alcohol) contained in the reflux stream. The solvent is recycled to the reactor 10. As can be seen from Fig. 1 some of the liquid in the reactor 10 is also fed to the distillation apparatus 16 so as to provide for continuous removal of the various oxygenated products which are not carried ofi as vapors and condensed in the reflux condenser 12.

While one specific example of the present invention has been given above, it is subject to wide variation without departing from the scope thereof. For example, the manganese propionate (of about 0.1% concentration) is a well-known oxidation catalyst. Other manganous salts or salts of oxides of metals of variable valence are equally effective. An important purpose of utilizing an oxidation catalyst is to prevent the creation of large concentrations of dangerously explosive hydroperoxides. It is believed that the metal walls of the reaction chamber may have sufiicient catalytic effect to prevent the formation of such hydroperoxides. Similarly, while the use of a phosphate buifer solution (which is obtained by titrating a solution of trisodium phosphate with phosphoric acid) is quite effective, numerous other well-known buffer solutions may be employed. Equally, the pH of the solution may be kept above about by use of an alkali such as sodium hydroxide which can be added as required during the reaction. The range of operating pressures and operating temperatures is quite broad and can be varied within considerable limits.

With regard to pressure it should be pointed out that it is preferably maintained above 300 lbs. per square inch, but that considerably higher pressures may be utilized where design considerations indicate the desirability of such higher pressures. The temperature within the reactor may be varied between about 150 C. and above 200 C. or higher.

The specific procedure described for the oxidation of isobutylene to isobutylene glycol can be applied to olefins in general. Other olefins which may be oxidized to their respective glycols are ethylene, propylene and amylenes.

While the invention has been described with particular reference to preferred embodiments thereof wherein controlled concentrations of the olefin feed have been employed to prevent substantial polymer formation, other techniques may be equally employed. For example, polymerization inhibitors can be incorporated in the reaction mass so as to substantially reduce the amount of polymeric material formed. One such inhibitor, which has been found to be very effective, is nitrobenzene. One method of using such an inhibitor is set forth in the following nonlirniting example:

Example Ill Fifteen hundred cubic centimeters of tertiary butyl alcohol (as a solvent) together with 1.4 grams of a manganese propionate catalyst, 40 cc. of a pH 5 phosphate buffer solution and 58.5 grams of nitrobenzene are charged to high pressure reactor 10. Eight hundred and fifty grams of isobutylene are now passed into the reactor and the temperature is raised to about 125 C.; air is fed until the pressure reaches 720 p. s. i., the temperature being raised to 177 C. during this addition. A steady rate of air feed of about 4 standard cubic feet per hour is maintained and isobutylene is fed in at varying rates to replenish the consumption. fed in this manner.

At the end of the reaction (about 6 hours) the reaction mixture is neutralized with a sodium hydroxide solution to a pH of 7 and then fractionated to yield the following products (indicated as grams of product per hundred grams of isobutylene consumed):

Acetone 26.0 grams; methallyl alcohol 13.02 grams; isobutylene glycol 58.2 grams; formic acid 3.11 grams; acetic acid 7.29 grams; isobutyric acid 2.8 grams; methanol 1.74 grams; Z-butanone 8.94 grams; methyl acetate 0.77 gram; isobutyl acetate 5.75 grams; carbon monoxide 7.07 grams; carbon dioxide 8.18 grams; and polymeric material 11.7 grams.

When utilizing nitrobenzene as a polymerization in- 160 grams of isobutylene are hibitor, it has been found that concentrations from about.

2% to 10% by weight of the solvent are satisfactory. It is possible that somewhat lower concentrations than 2% may be effective, but it is preferred to operate in the above range. While concentrations of above 10% may be employed, it is not necessary and has only the effect of producing greater amounts of nitrobenzene degradation products. The consumption of nitrobenzene naturally,

. in this case, would add to the cost of the final products.

When the polymerization inhibitor (i. e., nitrobenzene) is not employed, the degree of polymer formation is on the same order of magnitude as occurred in Example II, other conditions, such as olefin concentration, being comparable and benzene used as a solvent in place of the tertiary butyl alcohol of Example II.

The above discussion of the invention has been primarily concerned with the oxidation of olefins to their corresponding glycol. The invention is equally applicable to the use of saturated hydrocarbons containing tertiary hydrocarbons, such as isobutane and the like, as starting materials. Fig. 2 is a flow sheet illustrating this aspect of the invention. As can be seen, like numbers in Fig. 2 correspond to like elements and steps in Fig. 1. In Fig. 2, however, the reactor serves the dual purpose of oxidizing both isobutane and isobutylene. In this embodiment of the invention, the isobutane is oxidized in benzene as a solvent to form tertiary butyl alcohol as the primary reaction product. This tertiary butyl alcohol is then dehydrated (at 18) to isobutylene by the use of a heated dehydrating agent such as aluminum oxide (A1203). The technique for utilizing such dehydration agents is well known and described in numerous texts such as page 52 of Chernjstry of Organic Compounds Conant and Blatt, published by MacMillan in November, 1947.

The method of operating the reactor 10 to produce tertiary butyl alcohol is set forth in the following nonlimiting example:

Example IV Thirteen hundred grams of benzene solvent together with 1.5 grams of manganese propionate catalyst are charged to high pressure reactor 10. 850 grams of isobutane are now passed in and the reactor temperature is raised to about 125 C. Air is fed until the pressure reaches about 700 p. s. i., the temperature during this addition being raised to about 185 C. A steady rate of air feed of about 4 standard cubic feet per hour is maintained and isobutane is fed at varying rates to replenish the consumption. 372 grams of isobutane are fed in this manner. At the end of the reaction (about 5 hours) the mixture is repeatedly extracted with water and fractionation of the water washings yields the following products (indicated as grams of product per hundred grams of isobutane consumed) Acetone 25.5 grams; tertiary butyl alcohol 80.1 grams; isobutyl alcohol 11.9 grams; acetic acid 4.9 grams; methanol 2.9 grams; 2-butanone 1.2 grams; carbon monoxide 5.3 grams; and carbon dioxide 6.5 grams.

The tertiary butyl alcohol is separated from the reaction products in the distillation separator 16 and is fed to a dehydration step 18 where the tertiary butyl alcohol is converted to isobutylene, which in turn may be oxidized in accordance with the technique described in Example I. If the process is to be run on a continuous basis, with a single reactor, the isobutylene is fed back to the same reactor in which the isobutane is oxidized to tertiary butyl alcohol. This is the modification of the invention shown in Fig. 2. The recycling of the various solvents and reactants is also shown in Fig. 2. In this connection it should be pointed out that oxygenated products are continuously removed while unreacted isobutane and isobutylene are continuously recycled. Equally, the tertiary butyl alcohol is continuously recycled (after it has been dehydrated to isobutylene).

In other respects the operation of the process of Fig. 2 is similar to that previously described in connection with the discussion of Fig. 1.

Since certain changes may be made in the above 6 process without departing from the scope of the invention herein invloved, it is intended that all matter contained in the above description, or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

A method of forming isobutylene glycol and tertiary butyl alcohol which comprises dissolving a mixture of isobutane and isobutylene in .an inert organic solvent, passing an elemental-oxygen-containing gas into said solution while said solution is held under superatmospheric pressure and maintained at a temperature above about C. to oxidize said isobutane to tertiary butyl alcohol and said isobutylene to isobutylene glycol, and recovering said tertiary butyl alcohol and isobutylene glycol.

References Cited in the file of this patent UNITED STATES PATENTS 1,875,312 Youtz Aug. 30, 1932 2,071,395 Dreyfus Feb. 23, 1937 2,265,948 Loder Dec. 9, 1941 2,316,604 Loder et al. Apr. 13, 1943 2,434,888 Rust et al. Jan. 20, 1948 2,437,648 Milas Mar. 9, 1948 2,475,605 Prutton et al July 12, 1948 2,500,599 Bergsteinsson Mar. 14, 1950 2,644,837 Schweitzer July 7, 1953 OTHER REFERENCES Bull. Soc. Chim. (5) 1 (1934) pgs. 130847.

Fette und Seifen: vol. 51, pgs. 3079 (1944) via Chem. Abs. vol. 44, 7567*.

Groggins: Unit Processes (3rd ed. 1947) McGraw- Hill Book Co., Inc., N. Y.; p. 452, Fette und Seifen & Bull. Soc. Chim.

Lucas & Pressman: Principles & Practice in Organic Chemistry (1949) John Wiley & Sons, Inc., N. Y. p. 10, 1st para. and pg. 147, section 14.17.

Jour. Chem. Soc. (London) 1949, pgs. 2998 and 2999 (Article by Mugdan et a1).

Fuson: Advanced Organic Chemistry (1950); Wiley & Sons, Inc., N. Y. pgs. 2201. 

